Vehicle height adjustment apparatus

ABSTRACT

A vehicle height adjustment apparatus includes a rear wheel suspension spring that is disposed between a vehicle body and a tire wheel of a vehicle; a rear wheel damper that undergoes an extensional and contractional operation so as to move working oil to dampen vibration of the spring; a support member that supports one end portion of the spring, and moves relative to the damper to change the length of the spring; a jack chamber into which the working oil causing the support member to move relative to the damper flows by the extensional and contractional operation of the damper; a rear wheel electromagnetic valve that adjusts the amount of the working oil flowing into the jack chamber by the degree of opening of the electromagnetic valve; and control device that controls the degree of opening of the electromagnetic valve based on a weight exerted on the vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2014-036448 filed on Feb. 27, 2014, theentire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle height adjustment apparatusthat adjusts a vehicle height of a motorcycle.

2. Description of Related Art

In recent years, an apparatus is proposed which increases the vehicleheight of a motorcycle while the motorcycle is travelling, and decreasesthe vehicle height in order for an occupant to easily get on and off themotorcycle at a stop.

For example, a vehicle height adjustment apparatus disclosed inJP-B-H08-22680 has the following configuration. That is, a rear arm ispivotably supported by a rear portion of a vehicle frame of themotorcycle, and a rear wheel is supported in a rear end of the rear armvia a vehicle axle. A hydraulic shock absorbing apparatus is disposedbetween the rear arm and the vehicle frame via a link mechanism. Thehydraulic shock absorbing apparatus has a hydraulic attenuator and ashock absorbing spring. A lid is fitted into a cylinder head aperture,and also functions as a bracket for attachment of a cylinder. A supporttube is fixed to the lid while being freely fitted in the circumferenceof the cylinder. A cylindrical spring seat is inserted in a fitting yetslidable manner into the cylinder and the support tube. The spring seatis intended to support the shock absorbing spring on the opposite sideof a bracket of a piston rod. A working oil chamber is formed on aninner side of the support tube. The vehicle height adjustment apparatuspushes the spring seat downwardly against the shock absorbing spring,and extends an oil pressure attenuator by changing the oil pressure ofthe working oil chamber. Accordingly, a gap between the rear arm and theframe is increased, and thus the vehicle height is increased.

SUMMARY OF THE INVENTION

In an apparatus that adjusts a vehicle height by changing an initiallength of a spring and thus an initial load, the vehicle height ischanged by a weight exerted on a vehicle such as the weight of anoccupant or the weight of luggage. For example, when the weight exertedon the vehicle is greater than an assumed weight, the vehicle heightbecomes lower than a desired height. When the weight exerted on thevehicle is less than the assumed weight, the vehicle height becomeshigher than the desired height. In particular, since the vehicle heightaffects ride comfort or travelling stability while the vehicle istravelling, obtaining the desired height regardless of the weightexerted on the vehicle is desired.

An object of the present invention is to provide a vehicle heightadjustment apparatus that can adjust a vehicle height to a desiredheight regardless of a weight exerted on a vehicle.

A vehicle height adjustment apparatus according to an aspect of thepresent invention includes a spring that is disposed between a vehiclebody and a tire wheel of a vehicle; a damper that undergoes anextensional and contractional operation so as to move working oil todampen vibration of the spring; a support member that supports one endportion of the spring, and moves relative to the damper to change thelength of the spring; a working oil chamber into which the working oilcausing the support member to move relative to the damper flows by theextensional and contractional operation of the damper; anelectromagnetic valve that adjusts the amount of the working oil flowinginto the working oil chamber by the degree of opening of theelectromagnetic valve; and a control unit that controls the degree ofopening of the electromagnetic valve based on a weight exerted on thevehicle.

Here, the control unit may change upper and lower limits of the amountof working oil flowing into the working oil chamber based on the weightexerted on the vehicle.

According to the present invention, it is possible to provide thevehicle height adjustment apparatus that can adjust the vehicle heightto a desired height regardless of the weight exerted on the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a schematic configuration of a motorcycleaccording to an embodiment.

FIG. 2 is a cross-sectional view of a rear suspension.

FIGS. 3A and 3B are views describing an operation of a rear wheel liquidsupply device.

FIGS. 4A and 4B are views describing adjustment of a vehicle height by arear wheel relative position changing device.

FIG. 5 is a view illustrating a mechanism in which the vehicle height ismaintained.

FIG. 6 is a cross-sectional view of a front fork.

FIGS. 7A and 7B are views describing an operation of a front wheelliquid supply device.

FIGS. 8A and 8B are views describing adjustment of the vehicle height bya front wheel relative position changing device.

FIG. 9 is a view illustrating a mechanism in which the vehicle height ismaintained.

FIG. 10A is a view illustrating a schematic configuration of a frontwheel electromagnetic valve, and FIG. 10B is a view illustrating aschematic configuration of a rear wheel electromagnetic valve.

FIG. 11 is a block diagram of a control device.

FIG. 12 is a block diagram of an electromagnetic valve controlleraccording to the embodiment.

FIG. 13 is an exterior appearance view of an input device.

FIG. 14A is a graph illustrating a correlation between a vehicle speedand a front wheel target movement, and FIG. 14B is a graph illustratinga correlation between the vehicle speed and a rear wheel targetmovement.

FIG. 15A is a graph illustrating a relationship between a weight exertedon the motorcycle and the front wheel target movement, and FIG. 15B is agraph illustrating a relationship between the weight exerted on themotorcycle and the rear wheel target movement.

FIG. 16A is a graph illustrating a relationship between the weightexerted on the motorcycle and the front wheel target movement, and FIG.16B is a graph illustrating a relationship between the weight exerted onthe motorcycle and the rear wheel target movement.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

FIG. 1 is a view illustrating a schematic configuration of a motorcycle1 according to an embodiment.

As illustrated in FIG. 1, the motorcycle 1 has a vehicle frame 11; ahead pipe 12 that is attached to a front end portion of the vehicleframe 11; two front forks 13 that are provided in the head pipe 12; anda front wheel 14 that is attached to lower ends of the two front forks13. The two front forks 13 are respectively disposed on right and leftsides of the front wheel 14. FIG. 1 illustrates only the front fork 13that is disposed on the right side. A specific configuration of thefront fork 13 will be described later.

The motorcycle 1 has a handlebar 15 that is attached to upper portionsof the front forks 13; a fuel tank 16 that is attached to a front upperportion of the vehicle frame 11; and an engine 17 and a transmission 18which are disposed below the fuel tank 16.

The motorcycle 1 has a seat 19 that is attached to a rear upper portionof the vehicle frame 11; a swing arm 20 that is swingably attached to alower portion of the vehicle frame 11; a rear wheel 21 that is attachedto a rear end of the swing arm 207 and one or two rear suspensions 22that are attached between a rear portion (the rear wheel 21) of theswing arm 20 and a rear portion of the vehicle frame 11. The one or thetwo rear suspensions 22 are respectively disposed on right and leftsides of the rear wheel 21. FIG. 1 illustrates only the rear suspension22 that is disposed on the right side. A specific configuration of therear suspension 22 will be described later.

The motorcycle 1 has ahead lamp 23 that is disposed in front of the headpipe 12; a front fender 24 that is attached to the front forks 13 so asto cover an upper portion of the front wheel 14; a tail lamp 25 that isdisposed in the back of the seat 19; and a rear fender 26 that isattached below the tail lamp 25 so as to cover an upper portion of therear wheel 21. The motorcycle 1 has a brake 27 for stopping the rotationof the front wheel 14.

The motorcycle 1 has a front wheel rotation detection sensor 31 thatdetects a rotation angle of the front wheel 14, and a rear wheelrotation detection sensor 32 that detects a rotation angle of the rearwheel 21. The motorcycle 1 has a load detection sensor 33 that detects aload exerted on the front wheel 14 and the rear wheel 21 from thevehicle frame 11 when an occupant gets on or luggage is mounted on theseat 19 and the like.

The motorcycle 1 includes a control device 50 as an example of thecontrol unit that controls the degree of opening of a front wheelelectromagnetic valve 270 of the front fork 13, which will be describelater and the degree of opening of a rear wheel electromagnetic valve170 of the rear suspension 22, which will be described later. Thecontrol device 50 controls a vehicle height of the motorcycle 1 bycontrolling the degree of opening of the front wheel electromagneticvalve 270 and the rear wheel electromagnetic valve 170 which will bedescribed later. The control device 50 receives signals output from thefront wheel rotation detection sensor 31, the rear wheel rotationdetection sensor 32, the load detection sensor 33, and the like.

Subsequently, the rear suspension 22 will be described.

FIG. 2 is a cross-sectional view of the rear suspension 22.

The rear suspension 22 is attached between the vehicle frame 11 as anexample of a vehicle body and the rear wheel 21 of the motorcycle 1. Therear suspension 22 includes a rear wheel suspension spring 110 as anexample of a spring that supports the weight of the motorcycle 1, andabsorbs an impact, and a rear wheel damper 120 as an example of a damperthat dampens vibration of the rear wheel suspension spring 110. The rearsuspension 22 includes a rear wheel relative position changing device140 that can change a rear wheel relative position indicating a relativeposition between the vehicle frame 11 and the rear wheel 21 by adjustingthe spring force of the rear wheel suspension spring 110, and a rearwheel liquid supply device 160 that supplies liquid to the rear wheelrelative position changing device 140. The rear suspension 22 includes avehicle body side attachment member 184 through which the rearsuspension 22 is attached to the vehicle frame 11; a vehicle axle-sideattachment member 185 through which the rear suspension 22 is attachedto the rear wheel 21; and a spring receiver 190 that is attached to thevehicle axle-side attachment member 185 so as to support one end portion(a lower portion in FIG. 2) of the rear wheel suspension spring 110 in acenterline direction. The rear suspension 22 functions as an example ofchange means that can change a relative position between the vehicleframe 11 and the rear wheel 21 as an example of a tire wheel, and as anexample of rear wheel-side change means.

As illustrated in FIG. 2, the rear wheel damper 120 includes a cylinder125 having a thin-wall cylindrical outer cylinder 121; a thin-wallcylindrical inner cylinder 122 that is accommodated in the outercylinder 121; a bottom cover 123 that blocks one end portion (a lowerportion in FIG. 2) of the cylindrical outer cylinder 121 in a centerlinedirection (in the vertical direction in FIG. 2) of the outer cylinder121; and an upper cover 124 that blocks one end portion (an upperportion in FIG. 2) of the inner cylinder 122 in the centerlinedirection. Hereinafter, the centerline direction of the outer cylinder121 is simply referred to as the “centerline direction”.

The rear wheel damper 120 includes a piston 126 that is inserted intothe inner cylinder 122 so as to be movable in the centerline direction,and a piston rod 127 that extends in the centerline direction, andsupports the piston 126 by one end portion (an upper end portion in FIG.2) of the piston rod 127 in the centerline direction. The piston 126 isin contact with an inner circumferential surface of the inner cylinder122, and divides a liquid (oil in the embodiment) sealed space in thecylinder 125 into a first oil chamber 131 and a second oil chamber 132.The first oil chamber 131 is positioned on one end side of the piston126 in the centerline direction, and the second oil chamber 132 ispositioned on the other end side of the piston 126 in the centerlinedirection. The piston rod 127 is a cylindrical member, and a pipe 161 tobe described later is inserted into the piston rod 127. In theembodiment, oil functions as an example of working oil.

The rear wheel damper 120 includes a first damping force generatingapparatus 128 that is disposed in one end portion of the piston rod 127in the centerline direction, and a second damping force generatingapparatus 129 that is disposed in the other end portion of the innercylinder 122 in the centerline direction. The first damping forcegenerating apparatus 128 and the second damping force generatingapparatus 129 dampen extensional and contractional vibration of thecylinder 125 and the piston rod 127, which is occurring when the rearwheel suspension spring 110 absorbs an impact force from a road surface.The first damping force generating apparatus 128 is disposed to functionas a connection path between the first oil chamber 131 and the secondoil chamber 132. The second damping force generating apparatus 129 isdisposed to function as a connection path between the second oil chamber132 and a jack chamber 142 of the rear wheel relative position changingdevice 140, which will be described later.

The rear wheel liquid supply device 160 undergoes a pumping operation byan extensional and contractional movement of the piston rod 127 relativeto the cylinder 125 so that the rear wheel liquid supply device 160supplies liquid into the jack chamber 142 of the rear wheel relativeposition changing device 140, which will be described later.

The rear wheel liquid supply device 160 has the cylindrical pipe 161that is fixed to the cover 124 of the rear wheel damper 120 so as toextend in the centerline direction. The pipe 161 is coaxially insertedinto a pump chamber 162 which is an inner portion of the cylindricalpiston rod 127.

The rear wheel liquid supply device 160 has a discharge check valve 163and a suction check valve 164. When the piston rod 127 moves to enterthe cylinder 125 and the pipe 161, liquid in the pump chamber 162 ispressurized and discharged into the jack chamber 142, which will bedescribed later, via the discharge check valve 163. When the piston rod127 moves to retract from the cylinder 125 and the pipe 161, a pressureof the pump chamber 162 becomes negative, and liquid in the cylinder 125is suctioned into the pump chamber 162 via the suction check valve 164.

FIGS. 3A and 3B are views describing an operation of the rear wheelliquid supply device 160.

When the rear suspension 22 receives a force caused by concave andconvex road surfaces while the motorcycle 1 is travelling, the rearwheel liquid supply device 160 with the aforementioned configurationundergoes a pumping operation by an extensional and contractionalmovement in which the piston rod 127 enters and retracts from thecylinder 125 and the pipe 161. When the pump chamber 162 is pressured bythe pumping operation, the discharge check valve 163 is opened by liquidin the pump chamber 162, and the liquid is discharged into the jackchamber 142 of the rear wheel relative position changing device 140(refer to FIG. 3A). When a pressure of the pump chamber 162 becomesnegative by the pumping operation, the suction check valve 164 is openedby liquid in the second oil chamber 132 of the cylinder 125, and theliquid is suctioned into the pump chamber 162 (refer to FIG. 3B).

The rear wheel relative position changing device 140 has a supportmember 141 that is disposed to cover an outer circumference of thecylinder 125 of the rear wheel damper 120, and supports the other endportion (an upper portion in FIGS. 3A and 3B) of the rear wheelsuspension spring 110 in the centerline direction. The rear wheelrelative position changing device 140 also has a hydraulic jack 143 thatis disposed to cover an outer circumference of one end portion (an upperportion in FIGS. 3A and 3B) of the cylinder 125 in the centerlinedirection, and forms the jack chamber 142 along with the support member141. When the jack chamber 142 as an example of a working oil chamber isfilled with liquid from the cylinder 125, or when liquid is dischargedfrom the jack chamber 142, the support member 141 moves relative to thehydraulic jack 143 in the centerline direction. The vehicle body sideattachment member 184 is attached to an upper portion of the hydraulicjack 143, and the support member 141 moves relative to the hydraulicjack 143 in the centerline direction. Accordingly, the spring force ofthe rear wheel suspension spring 110 changes, thereby changing aposition of the seat 19 relative to the rear wheel 21.

The rear wheel relative position changing device 140 has a rear wheelelectromagnetic valve 170 which is an electromagnetic valve (a solenoidvalve) provided in a fluid flow path between the jack chamber 142 and aliquid reservoir chamber 143 a formed in the hydraulic jack 143. Whenthe rear wheel electromagnetic valve 170 is closed, liquid supplied intothe jack chamber 142 is reserved in the jack chamber 142. When the rearwheel electromagnetic valve 170 is open, the liquid supplied into thejack chamber 142 is discharged into the liquid reservoir chamber 143 aformed in the hydraulic jack 143. The rear wheel electromagnetic valve170 will be described in detail later. The liquid discharged into theliquid reservoir chamber 143 a returns into the cylinder 125.

FIGS. 4A and 4B are views describing adjustment of a vehicle height bythe rear wheel relative position changing device 140.

When the rear wheel liquid supply device 160 supplies liquid into thejack chamber 142 in a state in which the rear wheel electromagneticvalve 170 is even a little closed from a fully open state, the jackchamber 142 is filled with the liquid, the support member 141 movestoward one end portion (a lower portion in FIG. 4A) of the hydraulicjack 143 in the centerline direction, and the spring length of the rearwheel suspension spring 110 becomes shortened (refer to FIG. 4A). Incontrast, when the rear wheel electromagnetic valve 170 is fully open,the liquid in the jack chamber 142 is discharged into the liquidreservoir chamber 143 a, the support member 141 moves toward the otherend portion (an upper portion in FIG. 4B) of the hydraulic jack 143 inthe centerline direction, and the spring length of the rear wheelsuspension spring 110 becomes lengthened (refer to FIG. 4B).

When the support member 141 moves relative to the hydraulic jack 143,and thus the spring length of the rear wheel suspension spring 110becomes shortened, the spring force of the rear wheel suspension spring110 to press the support member 141 increases further compared to whenthe support member 141 does not move relative to the hydraulic jack 143.As a result, even when a force is exerted toward the rear wheel 21 fromthe vehicle frame 11, an initial load changes, at which a relativeposition between the rear wheel 21 and the vehicle frame 11 does notchange. At this time, when the same force is exerted from the vehicleframe 11 (the seat 19) toward one end portion (lower portions in FIGS.4A and 4B) of the rear suspension 22 in the centerline direction, theamount of compression (a change in distance between the vehicle bodyside attachment member 184 and the vehicle axle-side attachment member185) of the rear suspension 22 decreases. When the support member 141moves relative to the hydraulic jack 143, and thus the spring length ofthe rear wheel suspension spring 110 becomes shortened, the height ofthe seat 19 is increased (the vehicle height is increased) furthercompared to when the support member 141 does not move relative to thehydraulic jack 143. That is, the degree of opening of the rear wheelelectromagnetic valve 170 decreases, and thus the vehicle height isincreased.

In contrast, when the support member 141 moves relative to the hydraulicjack 143, and thus the spring length of the rear wheel suspension spring110 becomes lengthened, the spring force of the rear wheel suspensionspring 110 to press the support member 141 decreases further compared towhen the support member 141 does not move relative to the hydraulic jack143. At this time, when the same force is exerted from the vehicle frame11 (the seat 19) toward one end portion (the lower portions in FIGS. 4Aand 4B) of the rear suspension 22 in the centerline direction, theamount of compression (a change in distance between the vehicle bodyside attachment member 184 and the vehicle axle-side attachment member185) of the rear suspension 22 increases. When the support member 141moves relative to the hydraulic jack 143, and thus the spring length ofthe rear wheel suspension spring 110 becomes lengthened, the height ofthe seat 19 decreases (the vehicle height decreases) further compared towhen the support member 141 does not move relative to the hydraulic jack143. That is, the vehicle height decreases to the extent that the degreeof opening of the rear wheel electromagnetic valve 170 increases.

The degree of opening of the rear wheel electromagnetic valve 170 iscontrolled by the control device 50.

When the rear wheel electromagnetic valve 170 is open, liquid suppliedinto the jack chamber 142 may be discharged into the first oil chamber131 and/or the second oil chamber 132 of the cylinder 125.

As illustrated in FIG. 2, a return path 121 a is provided in the outercylinder 121 of the cylinder 125. When the support member 141 moves to apredetermined limit position toward one end portion (the lower portionin FIG. 2) of the hydraulic jack 143 in the centerline direction, liquidin the jack chamber 142 returns into the cylinder 125 via the returnpath 121 a.

FIG. 5 is a view illustrating a mechanism in which the vehicle height ismaintained.

When the rear wheel electromagnetic valve 170 is fully closed, andliquid is continuously supplied into the jack chamber 142, the suppliedliquid returns into the cylinder 125 via the return path 121 a.Accordingly, the position of the support member 141 is maintainedrelative to the hydraulic jack 143, and the height of the seat 19 (thevehicle height) is maintained.

Hereinafter, when the rear wheel electromagnetic valve 170 is fullyopen, and the amount of movement of the support member 141 relative tothe hydraulic jack 143 is the minimum (zero), the state of the rearsuspension 22 is referred to as a minimum state. When the rear wheelelectromagnetic valve 170 is fully closed, and the amount of movement ofthe support member 141 relative to the hydraulic jack 143 is themaximum, the state of the rear suspension 22 is referred to as a maximumstate.

The rear suspension 22 has a rear wheel relative position detection unit195 (refer to FIG. 11). The rear wheel relative position detection unit195 can detect the amount of movement of the support member 141 relativeto the hydraulic jack 143 in the centerline direction, or in otherwords, the amount of movement of the support member 141 relative to thevehicle body side attachment member 184 in the centerline direction.Specifically, coils are wound around an outer circumferential surface ofthe support member 141, and the hydraulic jack 143 is formed of amagnetic body. The rear wheel relative position detection unit 195 candetect the amount of movement of the support member 141 based onimpedance of the coils, which changes according to the movement of thesupport member 141 relative to the hydraulic jack 143 in the centerlinedirection.

Subsequently, the front fork 13 will be described in detail.

FIG. 6 is a cross-sectional view of the front fork 13.

The front fork 13 is attached between the vehicle frame 11 and the frontwheel 14. The front fork 13 includes a front wheel suspension spring 210that supports the weight of the motorcycle 1, and absorbs an impact, anda front wheel damper 220 that dampens vibration of the front wheelsuspension spring 210. The front fork 13 includes a front wheel relativeposition changing device 240 that can change a front wheel relativeposition indicating a relative position between the vehicle frame 11 andthe front wheel 14 by adjusting the spring force of the front wheelsuspension spring 210, and a front wheel liquid supply device 260 thatsupplies liquid to the front wheel relative position changing device240. The front fork 13 includes a vehicle axle-side attachment portion285 and a head pipe-side attachment portion (not illustrated). The frontfork 13 is attached to the front wheel 14 via the vehicle axle-sideattachment portion 285, and the front fork 13 is attached to the headpipe 12 via the head pipe-side attachment portion. The front fork 13functions as an example of the change means that changes a relativeposition between the vehicle frame 11 and the front wheel 14. The frontfork 13 functions as an example of the change means that can change arelative position between the vehicle frame 11 and the front wheel 14 asan example of the tire wheel, and as an example of front wheel-sidechange means.

As illustrated in FIG. 6, the front wheel damper 220 includes a cylinder225 having a thin-wall cylindrical outer cylinder 221; a thin-wallcylindrical inner cylinder 222, one end portion (a lower portion in FIG.6) of which is inserted into the cylindrical outer cylinder 221 via oneend portion (an upper portion in FIG. 6) of the outer cylinder 221 in acenterline direction (in the vertical direction in FIG. 6); a bottomcover 223 that blocks the other end portion (a lower portion in FIG. 6)of the outer cylinder 221 in the centerline direction; and an uppercover 224 that blocks the other end portion (an upper portion in FIG. 6)of the inner cylinder 222 in the centerline direction. The innercylinder 222 is slidably inserted into the outer cylinder 221.

The front wheel damper 220 includes a piston rod 227 that is attached tothe bottom cover 223 so as to extend in the centerline direction. Thepiston rod 227 has a cylindrical portion 227 a that extends in thecenterline direction, and a disc-shaped flange portion 227 b that isprovided in one end portion (an upper portion in FIG. 6) of thecylindrical portion 227 a in the centerline direction.

The front wheel damper 220 is fixed to one end portion (the lowerportion in FIG. 6) of the inner cylinder 222 in the centerlinedirection, and includes a piston 226 that is slidable relative to anouter circumference of the cylindrical portion 227 a of the piston rod227. The piston 226 is in contact with an outer circumferential surfaceof the cylindrical portion 227 a of the piston rod 227, and divides aliquid (oil in the embodiment) sealed space in the cylinder 225 into afirst oil chamber 231 and a second oil chamber 232. The first oilchamber 231 is positioned on one end side of the piston 226 in thecenterline direction, and the second oil chamber 232 is positioned onthe other end side of the piston 226 in the centerline direction. In theembodiment, oil functions as an example of working oil.

The front wheel damper 220 includes a cover member 230 that is providedabove the piston rod 227 so as to cover an aperture of the cylindricalportion 227 a of the piston rod 227. The cover member 230 supports oneend portion (a lower portion in FIG. 6) of the front wheel suspensionspring 210 in the centerline direction. The front wheel damper 220 hasan oil reservoir chamber 233 including a space that is formed in theinner cylinder 222 on one end side of the cover member 230 in thecenterline direction, and a space that is formed in the cylindricalportion 227 a of the piston rod 227. The oil reservoir chamber 233communicates with the first oil chamber 231 and the second oil chamber232 all the time.

The front wheel damper 220 includes a first dampening force generationportion 228 that is provided in the piston 226, and a second dampeningforce generation portion 229 that is formed in the piston rod 227. Thefirst dampening force generation portion 228 and the second dampeningforce generation portion 229 dampen extensional and contractionalvibration of the inner cylinder 222 and the piston rod 227, which isoccurring when the front wheel suspension spring 210 absorbs an impactforce from a road surface. The first dampening force generation portion228 is disposed to function as a connection path between the first oilchamber 231 and the second oil chamber 232. The second dampening forcegeneration portion 229 is formed to function as a connection pathbetween the first oil chamber 231, the second oil chamber 232 and theoil reservoir chamber 233.

The front wheel liquid supply device 260 undergoes a pumping operationby an extensional and contractional movement of the piston rod 227relative to the inner cylinder 222 so that the front wheel liquid supplydevice 260 supplies liquid into a jack chamber 242 of the front wheelrelative position changing device 240, which will be described later.

The front wheel liquid supply device 260 has a cylindrical pipe 261 thatis fixed to the cover member 230 of the front wheel damper 220 so as toextend in the centerline direction. The pipe 261 is coaxially insertedinto a pump chamber 262 which is an inner portion of a lower cylindricalportion 241 a of a support member 241 of the front wheel relativeposition changing device 240, which will be described later.

The front wheel liquid supply device 260 has a discharge check valve 263and a suction check valve 264. When the piston rod 227 moves to enterthe inner cylinder 222, liquid in the pump chamber 262 is pressurizedand discharged into the jack chamber 242, which will be described later,via the discharge check valve 263. When the piston rod 227 moves toretract from the inner cylinder 222, a pressure of the pump chamber 262becomes negative, and liquid in the oil reservoir chamber 233 issuctioned into the pump chamber 262 via the suction check valve 264.

FIGS. 7A and 7B are views describing an operation of the front wheelliquid supply device 260.

When the front fork 13 receives a force caused by concave and convexroad surfaces while the motorcycle 1 is travelling, and thus the pistonrod 227 enters and retracts from the inner cylinder 222, the pipe 261enters and retracts from the support member 241 of the front wheelrelative position changing device 240. Accordingly, the front wheelliquid supply device 260 with the aforementioned configuration undergoesa pumping operation. When the pump chamber 262 is pressured by thepumping operation, the discharge check valve 263 is opened by liquid inthe pump chamber 262, and the liquid is discharged into the jack chamber242 of the front wheel relative position changing device 240 (refer toFIG. 7A). When a pressure of the pump chamber 262 becomes negative bythe pumping operation, the suction check valve 264 is opened by liquidin the oil reservoir chamber 233, and the liquid is suctioned into thepump chamber 262 (refer to FIG. 7B).

The front wheel relative position changing device 240 includes thesupport member 241 that is disposed in the inner cylinder 222 of thefront wheel damper 220, and supports the other end portion (an upperportion in FIGS. 7A and 7B) of the front wheel suspension spring 210 inthe centerline direction via a disc-shaped spring receiver 244. Thesupport member 241 has the cylindrical lower cylindrical portion 241 aformed in one end portion (a lower portion in FIGS. 7A and 7B) of thesupport member 241 in the centerline direction, and a cylindrical uppercylindrical portion 241 b formed in the other end portion (an upperportion in FIGS. 7A and 7B) of the support member 241 in the centerlinedirection. The pipe 261 is inserted into the lower cylindrical portion241 a.

The front wheel relative position changing device 240 has a hydraulicjack 243 that is fitted into the upper cylindrical portion 241 b of thesupport member 241, and forms the jack chamber 242 along with thesupport member 241. When the jack chamber 242 is filled with liquid fromthe cylinder 225, or when liquid is discharged from the jack chamber242, the support member 241 moves relative to the hydraulic jack 243 inthe centerline direction. The head pipe-side attachment portion (notillustrated) is attached to an upper portion of the hydraulic jack 243,and the support member 241 moves relative to the hydraulic jack 243 inthe centerline direction. Accordingly, the spring force of the frontwheel suspension spring 210 changes, thereby changing a position of theseat 19 relative to the front wheel 14.

The front wheel relative position changing device 240 has a front wheelelectromagnetic valve 270 which is an electromagnetic valve (a solenoidvalve) provided in a fluid flow path between the jack chamber 242 andthe oil reservoir chamber 233. When the front wheel electromagneticvalve 270 is closed, liquid supplied into the jack chamber 242 isreserved in the jack chamber 242. When the front wheel electromagneticvalve 270 is open, the liquid supplied into the jack chamber 242 isdischarged into the oil reservoir chamber 233. The front wheelelectromagnetic valve 270 will be described in detail later.

FIGS. 8A and 8B are views describing adjustment of the vehicle height bythe front wheel relative position changing device 240.

When the front wheel liquid supply device 260 supplies liquid into thejack chamber 242 in a state in which the front wheel electromagneticvalve 270 is even a little closed from a fully open state, the jackchamber 242 is filled with the liquid, the support member 241 movestoward one end portion (a lower portion in FIG. 8A) of the hydraulicjack 243 in the centerline direction, and the spring length of the frontwheel suspension spring 210 becomes shortened (refer to FIG. 8A). Incontrast, when the front wheel electromagnetic valve 270 is fully open,the liquid in the jack chamber 242 is discharged into the oil reservoirchamber 233, the support member 241 moves toward the other end portion(an upper portion in FIG. 8B) of the hydraulic jack 243 in thecenterline direction, and the spring length of the front wheelsuspension spring 210 becomes lengthened (refer to FIG. 8B).

When the support member 241 moves relative to the hydraulic jack 243,and thus the spring length of the front wheel suspension spring 210becomes shortened, the spring force of the front wheel suspension spring210 to press the support member 241 increases further compared to whenthe support member 241 does not move relative to the hydraulic jack 243.As a result, even when a force is exerted toward the front wheel 14 fromthe vehicle frame 11, an initial load changes, at which a relativeposition between the front wheel 14 and the vehicle frame 11 does notchange. At this time, when the same force is exerted from the vehicleframe 11 (the seat 19) toward one end portion (lower portions in FIGS.8A and 8B) of the front fork 13 in the centerline direction, the amountof compression (a change in distance between the head pipe-sideattachment member (not illustrated) and the vehicle axle-side attachmentportion 285) of the front fork 13 decreases. When the support member 241moves relative to the hydraulic jack 243, and thus the spring length ofthe front wheel suspension spring 210 becomes shortened, the height ofthe seat 19 is increased (the vehicle height is increased) furthercompared to when the support member 241 does not move relative to thehydraulic jack 243. That is, the degree of opening of the front wheelelectromagnetic valve 270 decreases, and thus the vehicle height isincreased.

In contrast, when the support member 241 moves relative to the hydraulicjack 243, and thus the spring length of the front wheel suspensionspring 210 becomes lengthened, the spring force of the front wheelsuspension spring 210 to press the support member 241 decreases furthercompared to when the support member 241 does not move relative to thehydraulic jack 243. At this time, when the same force is exerted fromthe vehicle frame 11 (the seat 19) toward one end portion (the lowerportions in FIGS. 8A and 8B) of the front fork 13 in the centerlinedirection, the amount of compression (a change in distance between thehead pipe-side attachment portion (not illustrated) and the vehicleaxle-side attachment portion 285) of the front fork 13 increases. Whenthe support member 241 moves relative to the hydraulic jack 243, andthus the spring length of the front wheel suspension spring 210 becomeslengthened, the height of the seat 19 decreases (the vehicle heightdecreases) further compared to when the support member 241 does not moverelative to the hydraulic jack 243. That is, the vehicle heightdecreases to the extent that the degree of opening of the front wheelelectromagnetic valve 270 increases.

The degree of opening of the front wheel electromagnetic valve 270 iscontrolled by the control device 50.

When the front wheel electromagnetic valve 270 is open, liquid suppliedinto the jack chamber 242 may be discharged into the first oil chamber231 and/or the second oil chamber 232.

FIG. 9 is a view illustrating a mechanism in which the vehicle height ismaintained.

As illustrated in FIG. 9, a return path (not illustrated) is provided inan outer circumferential surface of the hydraulic jack 243. When thesupport member 241 moves to a predetermined limit position toward oneend portion (the lower portions in FIGS. 8A and 8B) of the hydraulicjack 243 in the centerline direction, liquid in the jack chamber 242returns into the oil reservoir chamber 233 via the return path.

When the front wheel electromagnetic valve 270 is closed, and liquid iscontinuously supplied into the jack chamber 242, the supplied liquidreturns into the oil reservoir chamber 233 via the return path.Accordingly, the position of the support member 241 is maintainedrelative to the hydraulic jack 243, or the height of the seat 19 (thevehicle height) is maintained.

Hereinafter, when the front wheel electromagnetic valve 270 is fullyopen, and the amount of movement of the support member 241 relative tothe hydraulic jack 243 is the minimum (zero), the state of the frontfork 13 is referred to as a minimum state. When the front wheelelectromagnetic valve 270 is fully closed, and the amount of movement ofthe support member 241 relative to the hydraulic jack 243 is themaximum, the state of the front fork 13 is referred to as a maximumstate.

The front fork 13 has a front wheel relative position detection unit 295(refer to FIG. 11). The front wheel relative position detection unit 295can detect the amount of movement of the support member 241 relative tothe hydraulic jack 243 in the centerline direction, or in other words,the amount of movement of the support member 241 relative to the headpipe-side attachment member in the centerline direction. Specifically,coils are wound around an outer circumferential surface in a radialdirection of the inner cylinder 222 at a position which corresponds tothe support member 241 in the centerline direction, and the supportmember 241 is formed of a magnetic body. The front wheel relativeposition detection unit 295 can detect the amount of movement of thesupport member 241 based on impedance of the coils, which changesaccording to the movement of the support member 241 relative to thehydraulic jack 243 in the centerline direction.

Subsequently, schematic configurations of the electromagnetic valveswill be described: the front wheel electromagnetic valve 270 of thefront wheel relative position changing device 240, and the rear wheelelectromagnetic valve 170 of the rear wheel relative position changingdevice 140.

FIG. 10A is a view illustrating the schematic configuration of the frontwheel electromagnetic valve 270, and FIG. 10B is a view illustrating theschematic configuration of a rear wheel electromagnetic valve 170.

The front wheel electromagnetic valve 270 is a so-called normally openelectromagnetic valve. As illustrated in FIG. 10A, the front wheelelectromagnetic valve 270 includes a bobbin 272 around which a coil 271is wound; a bar-shaped stator core 273 that is fixed to a hollow portion272 a of the bobbin 272; a holder 274 that supports the coil 271, thebobbin 272, and the stator core 273; and a substantially disc-shapedmoving core 275 that is disposed to correspond to a tip (an end surface)of the stator core 273, and is drawn toward the stator core 273. Thefront wheel electromagnetic valve 270 includes a valve body 276 which isfixed to the center of the tip of the moving core 275; a body 277 whichis assembled with the holder 274; a valve chamber 278 which is formed inthe body 277, and in which the valve body 276 is disposed; a covermember 279 which covers an aperture portion formed in the body 277, andforms the valve chamber 278 along with the body 277; and a coil spring280 which is disposed between the valve body 276 and the cover member279. The front wheel electromagnetic valve 270 includes a valve seat 281which is formed in the body 277, and is disposed in the valve chamber278 so as to correspond to the valve body 276; an introduction flow path282 which is formed in the body 277, and through which liquid isintroduced into the valve chamber 278 from the jack chamber 242 (referto FIG. 9); and an output flow path 283 which is formed in the body 277,and through which liquid is output into the oil reservoir chamber 233from the valve chamber 278 via the valve seat 281. The front wheelelectromagnetic valve 270 may be a normally closed electromagneticvalve.

The rear wheel electromagnetic valve 170 is a so-called normally openelectromagnetic valve. As illustrated in FIG. 10B, the rear wheelelectromagnetic valve 170 includes a bobbin 172 around which a coil 171is wound; a bar-shaped stator core 173 that is fixed to a hollow portion172 a of the bobbin 172; a holder 174 that supports the coil 171, thebobbin 172, and the stator core 173; and a substantially disc-shapedmoving core 175 that is disposed to correspond to a tip (an end surface)of the stator core 173, and is drawn toward the stator core 173. Therear wheel electromagnetic valve 170 includes a valve body 176 which isfixed to the center of the tip of the moving core 175; a body 177 whichis assembled with the holder 174; a valve chamber 178 which is formed inthe body 177, and in which the valve body 176 is disposed; a covermember 179 which covers an aperture portion formed in the body 177, andforms the valve chamber 178 along with the body 177; and a coil spring180 which is disposed between the valve body 176 and the cover member179. The rear wheel electromagnetic valve 170 includes a valve seat 181which is formed in the body 177, and is disposed in the valve chamber178 so as to correspond to the valve body 176; an introduction flow path182 which is formed in the body 177, and through which liquid isintroduced into the valve chamber 178 from the jack chamber 142 (referto FIG. 5); and an output flow path 183 which is formed in the body 177,and through which liquid is output into the liquid reservoir chamber 143a from the valve chamber 178 via the valve seat 181. The rear wheelelectromagnetic valve 170 may be a normally closed electromagneticvalve.

In the front wheel electromagnetic valve 270 and the rear wheelelectromagnetic valve 170 with the aforementioned configuration, whenthe coils 271 and 171 are not energized, the moving cores 275 and 175are respectively biased toward the bottom in FIGS. 10A and 10B by thecoil springs 280 and 180, and thus the valve bodies 276 and 176 are notin contact with the valve seats 281 and 181, respectively. The valvebodies 276 and 176 are respectively fixed to the tips (the end surfaces)of the moving cores 275 and 175. For this reason, the introduction flowpaths 282 and 182 communicate with the output flow paths 283 and 183,respectively, and the front wheel electromagnetic valve 270 and the rearwheel electromagnetic valve 170 are open. In contrast, in the frontwheel electromagnetic valve 270 and the rear wheel electromagnetic valve170, when the coils 271 and 171 are energized and thus magnetized, themoving cores 275 and 175 are respectively displaced based on balancebetween an induction force of the stator core 273 and a bias force ofthe coil spring 280, and balance between an induction force of thestator core 173 and a bias force of the coil spring 180. The front wheelelectromagnetic valve 270 and the rear wheel electromagnetic valve 170adjust positions of the valve bodies 276 and 176 relative to the valveseats 281 and 181, respectively. That is, the front wheelelectromagnetic valve 270 and the rear wheel electromagnetic valve 170adjust the degree of opening of the valves, respectively. The degree ofopening of the valves is respectively adjusted by changes in electricpower (current and voltage) supplied to the coils 271 and 171.

Subsequently, the control device 50 will be described.

FIG. 11 is a block diagram of a control device 50.

The control device 50 includes a CPU; a ROM that stores a program whichis executed by the CPU, various data and the like; a RAM that is used asa CPU's working memory and the like, and an EEPROM which is anon-volatile memory. The control device 50 receives signals output fromthe front wheel rotation detection sensor 31; the rear wheel rotationdetection sensor 32; the front wheel relative position detection unit295; the rear wheel relative position detection unit 195; and the like.

The control device 50 includes a front wheel rotation speed calculationunit 51 and a rear wheel rotation speed calculation unit 52. The frontwheel rotation speed calculation unit 51 calculates a rotation speed ofthe front wheel 14 based on a signal output from the front wheelrotation detection sensor 31. The rear wheel rotation speed calculationunit 52 that calculates a rotation speed of the rear wheel 21 based on asignal output from the rear wheel rotation detection sensor 32. Thefront wheel rotation speed calculation unit 51 and the rear wheelrotation speed calculation unit 52 acquire rotation angles of the frontwheel 14 and the rear wheel 21 respectively based on pulse signals whichare the signals output from the sensors, and then calculate rotationspeeds by differentiating the acquired rotation angles over elapsedtimes.

The control device 50 includes a front wheel movement acquisition unit53 that acquires a front wheel movement Lf based on a signal output fromthe front wheel relative position detection unit 295. The front wheelmovement Lf is the amount of movement of the support member 241 of thefront wheel relative position changing device 240 (refer to FIGS. 8A and8B) relative to the hydraulic jack 243. The control device 50 includes arear wheel movement acquisition unit 54 that acquires a rear wheelmovement Lr based on a signal output from the rear wheel relativeposition detection unit 195. The rear wheel movement Lr is the amount ofmovement of the support member 141 of the rear wheel relative positionchanging device 140 relative to the hydraulic jack 143. The front wheelmovement acquisition unit 53 and the rear wheel movement acquisitionunit 54 can acquire the front wheel movement Lf and the rear wheelmovement Lr respectively based on respective correlations between theimpedance of the coil that is stored in the ROM in advance, and thefront wheel movement Lf, and between the impedance of the coil that isstored in the ROM in advance, and the rear wheel movement Lr.

The control device 50 includes a vehicle speed acquisition unit 56 thatacquires a vehicle speed Vc, which is a moving speed of the motorcycle1, based on the rotation speed of the front wheel 14 calculated by thefront wheel rotation speed calculation unit 51 and/or the rotation speedof the rear wheel 21 calculated by the rear wheel rotation speedcalculation unit 52. The vehicle speed acquisition unit 56 acquires thevehicle speed Vc by calculating a moving speed of the front wheel 14 ora moving speed of the rear wheel 21 based on a front wheel rotationspeed Rf or a rear wheel rotation speed Rr. The moving speed of thefront wheel 14 can be calculated based on the front wheel rotation speedRf and the outer diameter of a tire of the front wheel 14. The movingspeed of the rear wheel 21 can be calculated based on the rear wheelrotation speed Rr and the outer diameter of a tire of the rear wheel 21.When the motorcycle 1 is normally travelling, it is possible tocomprehend that the vehicle speed Vc is equal to the moving speed of thefront wheel 14 or the moving speed of the rear wheel 21. The vehiclespeed acquisition unit 56 may acquire the vehicle speed Vc bycalculating an average moving speed of the front wheel 14 and the rearwheel 21 based on an average value of the front wheel rotation speed Rfand the rear wheel rotation speed Rr.

The control device 50 has an electromagnetic valve controller 57 thatcontrols the degree of opening of the front wheel electromagnetic valve270 of the front wheel relative position changing device 240 and thedegree of opening of the rear wheel electromagnetic valve 170 of therear wheel relative position changing device 140 based on the vehiclespeed Vc acquired by the vehicle speed acquisition unit 56. Theelectromagnetic valve controller 57 will be described in detail later.

The CPU executes software stored in a storage area such as the ROM so asto realize the front wheel rotation speed calculation unit 51, the rearwheel rotation speed calculation unit 52, the front wheel movementacquisition unit 53, the rear wheel movement acquisition unit 54, thevehicle speed acquisition unit 56, and the electromagnetic valvecontroller 57.

Subsequently, the electromagnetic valve controller 57 of the controldevice 50 will be described in detail.

FIG. 12 is a block diagram of the electromagnetic valve controller 57according to the embodiment.

The electromagnetic valve controller 57 has a target movementdetermination unit 570. The target movement determination unit 570 has afront wheel target movement determination unit 571 that determines afront wheel target movement which is a target movement of the frontwheel movement Lf; and a rear wheel target movement determination unit572 that determines a rear wheel target movement which is a targetmovement of the rear wheel movement Lr; and a weight acquisition unit575 that acquires the weight exerted on the motorcycle 1 as an exampleof the vehicle. The electromagnetic valve controller 57 has a targetcurrent determination unit 510 and a controller 520. The target currentdetermination unit 510 determines a target current supplied to the frontwheel electromagnetic valve 270 of the front wheel relative positionchanging device 240, and a target current supplied to the rear wheelelectromagnetic valve 170 of the rear wheel relative position changingdevice 140. The controller 520 performs a feedback control based on thetarget currents determined by the target current determination unit 510.

The target movement determination unit 570 determines a target movementbased on the vehicle speed Vc acquired by the vehicle speed acquisitionunit 56 (refer to FIG. 11) and the weight exerted on the motorcycle 1which is acquired by the weight acquisition unit 575.

The weight acquisition unit 575 acquires the weight exerted on themotorcycle 1 based on the weight input via the input device 34 that isprovided on the motorcycle 1.

FIG. 13 is an exterior appearance view of the input device 34.

For example, as illustrated in FIG. 13, the input device 34 is aso-called dial-type device having weight numerals written thereon. Auser can select the weight exerted on the motorcycle 1 by rotating aknob of the input device 34. A driver estimates the weight exerted onthe motorcycle 1 in consideration of the weight of an occupant on themotorcycle 1 or luggage to be carried by the motorcycle 1, and thedriver selects the weight via the input device 34. The weightacquisition unit 575 acquires the weight selected via the input device34 as the weight exerted on the motorcycle 1. For example, the inputdevice 34 may be provided in the vicinity of a speedometer.

FIG. 14A is a graph illustrating a correlation between the vehicle speedVc and the front wheel target movement, and FIG. 14B is a graphillustrating a correlation between the vehicle speed Vc and the rearwheel target movement.

FIG. 15A is a graph illustrating a relationship between the weightexerted on the motorcycle 1 and the front wheel target movement Lf0, andFIG. 15B is a graph illustrating a relationship between the weightexerted on the motorcycle 1 and the rear wheel target movement Lr0.

When the motorcycle 1 begins to travel, and the vehicle speed Vcacquired by the vehicle speed acquisition unit 56 is lower than apredetermined increasing vehicle speed Vu, the target movementdetermination unit 570 sets the target movement to zero. When thevehicle speed Vc increases from a vehicle speed lower than theincreasing vehicle speed Vu to a vehicle speed higher than or equal tothe increasing vehicle speed Vu, the target movement determination unit570 sets the target movement to a value that is determined in advancebased on the weight exerted on the motorcycle 1, which is acquired bythe weight acquisition unit 575. More specifically, as illustrated inFIG. 14A, when the vehicle speed Vc increases from a vehicle speed lowerthan the increasing vehicle speed Vu to a vehicle speed higher than orequal to the increasing vehicle speed Vu, the front wheel targetmovement determination unit 571 sets the front wheel target movement toa predetermined front wheel target movement Lf0 that is determined inadvance based on the weight exerted on the motorcycle 1 as illustratedin FIG. 15A. In contrast, as illustrated in FIG. 14B, when the vehiclespeed Vc increases from a vehicle speed lower than the increasingvehicle speed Vu to a vehicle speed higher than or equal to theincreasing vehicle speed Vu, the rear wheel target movementdetermination unit 572 sets the rear wheel target movement to apredetermined rear wheel target movement Lr0 that is determined inadvance based on the weight exerted on the motorcycle 1 as illustratedin FIG. 15B. Thereafter, while the vehicle speed Vc acquired by thevehicle speed acquisition unit 56 is higher than or equal to theincreasing vehicle speed Vu, the front wheel target movementdetermination unit 571 and the rear wheel target movement determinationunit 572 set the front wheel target movement and the rear wheel targetmovement to the predetermined front wheel target movement Lf0 and thepredetermined rear wheel target movement Lr0, respectively. The ROMstores in advance a relationship between a selected position of theinput device 34 and the weight exerted on the motorcycle 1, arelationship between the weight exerted on the motorcycle 1 and thefront wheel target movement Lf0 as illustrated in FIG. 15A, and arelationship between the weight exerted on the motorcycle 1 and the rearwheel target movement Lr0 as illustrated in FIG. 15B. Since the vehicleheight of the motorcycle 1 is determined based on the front wheelmovement Lf and the rear wheel movement Lr, the front wheel targetmovement Lf0 and the rear wheel target movement Lr0 can be determined inadvance based on the weight (a selected position of the input device 34)exerted on the motorcycle 1 in such a manner that the vehicle heightbecomes equal to a predetermined desired vehicle height, and thepredetermined front wheel target movement Lf0 and the pretermined rearwheel target movement Lr0 can be stored in the ROM.

In contrast, when the travelling speed of the motorcycle 1 decreasesfrom a vehicle speed higher than or equal to the increasing vehiclespeed Vu to a vehicle speed lower than or equal to a predetermineddecreasing vehicle speed Vd, the target movement determination unit 570sets the target movement to zero. That is, the front wheel targetmovement determination unit 571 and the rear wheel target movementdetermination unit 572 set the front wheel target movement and the rearwheel target movement to zero, respectively. It is possible toillustrate 10 km/h and 8 km/h for the increasing vehicle speed Vu andthe decreasing vehicle speed Vd, respectively.

Even in a case in which the vehicle speed Vc acquired by the vehiclespeed acquisition unit 56 is higher than the decreasing vehicle speedVd, when the motorcycle 1 decelerates rapidly due to the suddenapplication of a brake and the like, the target movement determinationunit 570 sets the target movement to zero. That is, the front wheeltarget movement determination unit 571 and the rear wheel targetmovement determination unit 572 set the front wheel target movement andthe rear wheel target movement to zero, respectively. The fact that themotorcycle 1 undergoes a rapid deceleration can be acquired based onwhether the amount of reduction of the vehicle speed Vc acquired by thevehicle speed acquisition unit 56 per unit time is less than or equal toa predetermined value.

The target current determination unit 510 has a front wheel targetcurrent determination unit 511 and a rear wheel target currentdetermination unit 512. The front wheel target current determinationunit 511 determines a front wheel target current based on the frontwheel target movement determined by the front wheel target movementdetermination unit 571. The front wheel target current is a targetcurrent of the front wheel electromagnetic valve 270. The rear wheeltarget current determination unit 512 determines a rear wheel targetcurrent based on the rear wheel target movement determined by the rearwheel target movement determination unit 572. The rear wheel targetcurrent is a target current of the rear wheel electromagnetic valve 170.

For example, the front wheel target current determination unit 511determines the front wheel target current by substituting the frontwheel target movement, which is determined by the front wheel targetmovement determination unit 571, into a corresponding map between thefront wheel target movement and the front wheel target current, andwhich is prepared based on an empirical rule and is stored in the ROM inadvance.

For example, the rear wheel target current determination unit 512determines the rear wheel target current by substituting the rear wheeltarget movement, which is determined by the rear wheel target movementdetermination unit 572, into a corresponding map between the rear wheeltarget movement and the rear wheel target current, and which is preparedbased on an empirical rule and is stored in the ROM in advance.

When the front wheel target movement and the rear wheel target movementare equal to zero, the front wheel target current determination unit 511and the rear wheel target current determination unit 512 set the frontwheel target current and the rear wheel target current to zero,respectively. In a state in which the front wheel target current and therear wheel target current are determined to be zero, when the frontwheel target movement and the rear wheel target movement which arerespectively determined by the front wheel target movement determinationunit 571 and the rear wheel target movement determination unit 572,change from zero to values other than zero, or in other words, when thevehicle height begins to be increased from a state of not beingincreased, the front wheel target current determination unit 511 and therear wheel target current determination unit 512 set the front wheeltarget current and the rear wheel target current, respectively, based onthe front wheel target movement and the rear wheel target movement whichare respectively determined by the front wheel target movementdetermination unit 571 and the rear wheel target movement determinationunit 572. When the front wheel electromagnetic valve 270 is a normallyclosed electromagnetic valve, and the front wheel target movement isequal to zero, it is necessary to energize the front wheelelectromagnetic valve 270. When the rear wheel electromagnetic valve 170is a normally closed electromagnetic valve, and the rear wheel targetmovement is equal to zero, it is necessary to energize the rear wheelelectromagnetic valve 170.

When the front wheel target current determination unit 511 determinesthe front wheel target current based on the front wheel target movementdetermined by the front wheel target movement determination unit 571,the front wheel target current determination unit 511 may perform afeedback control based on a deviation between the front wheel targetmovement determined by the front wheel target movement determinationunit 571 and the actual front wheel movement Lf acquired by the frontwheel movement acquisition unit 53 (refer to FIG. 11), and the frontwheel target current determination unit 511 may determine the frontwheel target current. Similarly, when the rear wheel target currentdetermination unit 512 determines the rear wheel target current based onthe rear wheel target movement determined by the rear wheel targetmovement determination unit 572, the rear wheel target currentdetermination unit 512 may perform a feedback control based on adeviation between the rear wheel target movement determined by the rearwheel target movement determination unit 572 and the actual rear wheelmovement Lr acquired by the rear wheel movement acquisition unit 54(refer to FIG. 11), and the rear wheel target current determination unit512 may determine the rear wheel target current.

The controller 520 has a front wheel operation controller 530 thatcontrols an operation of the front wheel electromagnetic valve 270; afront wheel electromagnetic valve drive unit 533 that drives the frontwheel electromagnetic valve 270; and a front wheel detection unit 534that detects an actual current flowing through the front wheelelectromagnetic valve 270. The controller 520 has a rear wheel operationcontroller 540 that controls an operation of the rear wheelelectromagnetic valve 170; a rear wheel electromagnetic valve drive unit543 that drives the rear wheel electromagnetic valve 170; and a rearwheel detection unit 544 that detects an actual current flowing throughthe rear wheel electromagnetic valve 170.

The front wheel operation controller 530 has a front wheel feedback(F/B) controller 531 and a front wheel PWM controller 532. The frontwheel feedback controller 531 performs a feedback control based on adeviation between the front wheel target current determined by the frontwheel target current determination unit 511 and an actual current (anactual front wheel current) detected by the front wheel detection unit534. The front wheel PWM controller 532 performs PWM control of thefront wheel electromagnetic valve 270.

The rear wheel operation controller 540 has a rear wheel feedback (F/B)controller 541 and a rear wheel PWM controller 542. The rear wheelfeedback controller 541 performs a feedback control based on a deviationbetween the rear wheel target current determined by the rear wheeltarget current determination unit 512 and an actual current (an actualrear wheel current) detected by the rear wheel detection unit 544. Therear wheel PWM controller 542 performs PWM control of the rear wheelelectromagnetic valve 170.

The front wheel feedback controller 531 obtains a deviation between thefront wheel target current and an actual front wheel current detected bythe front wheel detection unit 534, and performs a feedback control insuch a manner that the deviation becomes zero. The rear wheel feedbackcontroller 541 obtains a deviation between the rear wheel target currentand an actual rear wheel current detected by the rear wheel detectionunit 544, and performs a feedback control in such a manner that thedeviation becomes zero. For example, the front wheel feedback controller531 can perform a proportional process and an integral process on thedeviation between the front wheel target current and the actual frontwheel current by using a proportional element and an integral element,respectively. The rear wheel feedback controller 541 can perform aproportional process and an integral process on the deviation betweenthe rear wheel target current and the actual rear wheel current by usinga proportional element and an integral element, respectively. Theprocessed values can be added by an addition calculation unit.Alternatively, for example, the front wheel feedback controller 531 canperform a proportional process, an integral process and a differentialprocess on the deviation between the front wheel target current and theactual front wheel current by using a proportional element, an integralelement and a differential element, respectively. The rear wheelfeedback controller 541 can perform a proportional process, an integralprocess and a differential process on the deviation between the rearwheel target current and the actual rear wheel current by using aproportional element, an integral element and a differential element,respectively. The processed values can be added by the additioncalculation unit.

The front wheel PWM controller 532 changes a duty ratio (=t/T×100(%)) ofa pulse width (t) to a certain period (T), and performs PWM control ofthe degree of opening (a voltage applied to the coil of the front wheelelectromagnetic valve 270) of the front wheel electromagnetic valve 270.When the PWM control is performed, a pulse-shaped voltage is applied tothe coil of the front wheel electromagnetic valve 270 based on the dutyratio. At this time, a current flowing through the coil 271 of the frontwheel electromagnetic valve 270 cannot trace the applied pulse-shapedvoltage due to the impedance of the coil 271, and an output of thecurrent is dull. The current flowing through the coil of the front wheelelectromagnetic valve 270 increases and decreases proportionally to theduty ratio. For example, when the front wheel target current is equal tozero, the front wheel PWM controller 532 can set the duty ratio to zero,and when the front wheel target current is equal to the maximum currentor a first target current A1 which will be described later, the frontwheel PWM controller 532 can set the duty ratio to 100%.

Similarly, the rear wheel PWM controller 542 changes a duty ratio, andperforms PWM control of the degree of opening (a voltage applied to thecoil of the rear wheel electromagnetic valve 170) of the rear wheelelectromagnetic valve 170. When the PWM control is performed, apulse-shaped voltage is applied to the coil 171 of the rear wheelelectromagnetic valve 170 based on the duty ratio, and a current flowingthrough the coil 171 of the rear wheel electromagnetic valve 170increases and decreases proportionally to the duty ratio. For example,when the rear wheel target current is equal to zero, the rear wheel PWMcontroller 542 can set the duty ratio to zero, and when the rear wheeltarget current is equal to the maximum current or a second targetcurrent A2 which will be described later, the rear wheel PWM controller542 can set the duty ratio to 100%.

For example, the front wheel electromagnetic valve drive unit 533includes a transistor (FET) as a switching element that is connectedbetween a positive line of a power supply and the coil of the frontwheel electromagnetic valve 270. The front wheel electromagnetic valvedrive unit 533 controls the driving of the front wheel electromagneticvalve 270 by driving a gate of the transistor and causing the transistorto undergo a switching operation. For example, the rear wheelelectromagnetic valve drive unit 543 includes a transistor that isconnected between a positive line of the power supply and the coil ofthe rear wheel electromagnetic valve 170. The rear wheel electromagneticvalve drive unit 543 controls the driving of the rear wheelelectromagnetic valve 170 by driving a gate of the transistor andcausing the transistor to undergo a switching operation.

The front wheel detection unit 534 detects an actual current flowingthrough the front wheel electromagnetic valve 270 from a voltageoccurring between opposite ends of a shunt resistance that is connectedto the front wheel electromagnetic valve drive unit 533. The rear wheeldetection unit 544 detects an actual current flowing through the rearwheel electromagnetic valve 170 from a voltage occurring betweenopposite ends of a shunt resistance that is connected to the rear wheelelectromagnetic valve drive unit 543.

In the motorcycle 1 with the aforementioned configuration, theelectromagnetic valve controller 57 of the control device 50 determinesthe target current based on the target movement associated with theweight exerted on the motorcycle 1, and performs PWM control in such amanner that actual currents supplied to the front wheel electromagneticvalve 270 and the rear wheel electromagnetic valve 170 become equal tothe determined target currents. That is, the front wheel PWM controller532 and the rear wheel PWM controller 542 of the electromagnetic valvecontroller 57 change the duty ratios, and thus control electric powersupplied to the coil 271 of the front wheel electromagnetic valve 270and the coil 171 of the rear wheel electromagnetic valve 170,respectively, and control the front wheel electromagnetic valve 270 andthe rear wheel electromagnetic valve 170 to open to an arbitrary degreeof opening, respectively. Accordingly, when the control device 50controls upper limits of the amount of liquid (oil) flowing into thejack chamber 242 and the jack chamber 142 by controlling the degree ofopening of the front wheel electromagnetic valve 270 and the rear wheelelectromagnetic valve 170, the control device 50 can change the targetmovements to the target movements which are determined based on theweight exerted on the motorcycle 1 as illustrated in FIGS. 15A and 15B.In the relationship between the weight exerted on the motorcycle 1 andthe target movement illustrated in FIGS. 15A and 15B, as the weightbecomes larger, the front wheel target movement Lf0 and the rear wheeltarget movement Lr0 become larger. Therefore, as the weight exerted onthe motorcycle 1 becomes larger, an initial load of each of the frontwheel suspension spring 210 and the rear wheel suspension spring 110becomes larger. When the weight exerted on the motorcycle 1 is large,the front fork 13 and the rear suspension 22 are unlikely to becompressed. In contrast, when the weight exerted on the motorcycle 1 issmall, the front fork 13 and the rear suspension 22 are likely to becompressed. It is possible to adjust the vehicle height to a desiredheight regardless of the weight exerted on the motorcycle 1. As aresult, even when the weight of a driver is heavy, or two occupants geton the motorcycle 1, or luggage is heavy, it is possible to adjust thevehicle height to a desired height while the vehicle is travelling, andthus it is possible to improve ride comfort or travelling stability. Thefront wheel PWM controller 532 and the rear wheel PWM controller 542 ofthe electromagnetic valve controller 57 may control the front wheelelectromagnetic valve 270 and the rear wheel electromagnetic valve 170,respectively, in such a manner that the detected movements coincide withthe target movements. At this time, the front wheel PWM controller 532and the rear wheel PWM controller 542 determine the target currentsbased on the target movements and the detected movements, respectively.

In the embodiment, when the motorcycle 1 begins to travel, and thevehicle speed Vc acquired by the vehicle speed acquisition unit 56increases from a vehicle speed lower than the increasing vehicle speedVu to a vehicle speed higher than or equal to the increasing vehiclespeed Vu, or when the motorcycle 1 begins to travel, and the vehiclespeed Vc decreases from a vehicle speed higher than or equal to theincreasing vehicle speed Vu to a vehicle speed lower than or equal tothe decreasing vehicle speed Vd, the target movement determination unit570 sets the target movement to zero. However, the present invention isnot limited to the embodiment. The minimum target movement may not beset to zero, and instead, the minimum target movement may be determinedbased on the weight exerted on the motorcycle 1.

FIG. 16A is a graph illustrating a relationship between the weightexerted on the motorcycle 1 and the front wheel target movement Lf0, andFIG. 16B is a graph illustrating a relationship between the weightexerted on the motorcycle 1 and the rear wheel target movement Lr0.

FIG. 16A illustrates the maximum target movement and the minimum targetmovement of the front wheel target movement Lf0, and FIG. 16Billustrates the maximum target movement and the minimum target movementof the rear wheel target movement Lr0. The maximum target movement ofthe front wheel target movement Lf0 illustrated in FIG. 16A is amovement equivalent to the front wheel target movement Lf0 illustratedin FIG. 15A. The maximum target movement of the rear wheel targetmovement Lr0 illustrated in FIG. 16B is a movement equivalent to therear wheel target movement Lr0 illustrated in FIG. 15B.

When the motorcycle 1 begins to travel, and the vehicle speed Vc islower than the increasing vehicle speed Vu, or when the motorcycle 1begins to travel, and the vehicle speed Vc decreases from a vehiclespeed higher than or equal to the increasing vehicle speed Vu to avehicle speed lower than or equal to the decreasing vehicle speed Vd,the target movement determination unit 570 sets the target movements tothe minimum target movements based on the weight exerted on themotorcycle 1 as illustrated in FIGS. 16A and 16B. In other words, whenthe control device 50 controls lower limits of the amount of liquid(oil) flowing into the jack chamber 242 and the jack chamber 142 bycontrolling the degree of opening of the front wheel electromagneticvalve 270 and the rear wheel electromagnetic valve 170, the controldevice 50 can change the minimum target movements to the targetmovements which are determined based on the weight exerted on themotorcycle 1 as illustrated in FIGS. 16A and 16B. Accordingly, while thevehicle is travelling at a low speed, the control device 50 can adjustthe vehicle height to a desired height regardless of the weight exertedon the motorcycle 1. As a result, even when the weight of a driver isheavy, two occupants get on the motorcycle 1, or luggage is heavy, it ispossible to adjust the vehicle height to a desired height while thevehicle is travelling at a low speed, and thus it is possible to improveride comfort or travelling stability.

Modification Example 1

In the embodiment, a so-called dial-type device is adopted as the inputdevice 34. However, the present invention is not limited to theembodiment. Insofar as a user can select the weight exerted on themotorcycle 1, the input device 34 may be a lever-type device in whichthe user linearly moves a knob, a switch-type device in which the userpresses a button for the weight, or a touch panel-type device in whichthe user presses a display on a screen so as to input the weight.

Modification Example 2

In the embodiment, the weight acquisition unit 575 acquires the weightexerted on the motorcycle 1 based on the weight input via the inputdevice 34 that is provided on the motorcycle 1. However, the presentinvention is not limited to the embodiment.

For example, a weight sensor may be provided in the seat 19 of themotorcycle 1, and the weight acquisition unit 575 may acquire the weightexerted on the motorcycle 1 based on the weight detected by the weightsensor. When the vehicle speed Vc is lower than the increasing vehiclespeed Vu before the vehicle height begins to be increased, the weightacquisition unit 575 can acquire the weight exerted on the motorcycle 1based on the value detected by the weight sensor.

For example, the weight acquisition unit 575 may acquire the weightexerted on the motorcycle 1 dependent on a changing speed of the amountof movement determined based on the front wheel movement Lf and the rearwheel movement Lr when a predetermined period of time elapses after thevehicle height begins to be increased from a state of not beingincreased.

Modification Example 3

When electric power is not supplied to the control device 50, forexample, the engine 17 of the motorcycle 1 is stopped, the EEPROM or thelike may store the weight exerted on the motorcycle 1, which is acquiredat a startup, and the weight acquisition unit 575 may read the storedweight at the next startup.

Modification Example 4

Each correlation between the weight exerted on the motorcycle 1 and thetarget movement, which is stored in the ROM as illustrated in FIGS. 15A,15B, 16A, and 16B, may undergo an offset correction for the motorcycle 1after the front fork 13 and the rear suspension 22 are attached to themotorcycle 1. Accordingly, it is possible to correct a variation of eachof the front fork 13 and the rear suspension 22.

What is claimed is:
 1. A vehicle height adjustment apparatus comprising:a spring that is disposed between a body of a vehicle and a tire wheelof the vehicle; a damper that undergoes an extensional and contractionaloperation so as to move working oil to dampen vibration of the spring; asupport member that supports one end portion of the spring, and movesrelative to the damper to change a length of the spring; a working oilchamber into which the working oil causing the support member to moverelative to the damper flows by the extensional and contractionaloperation of the damper; an electromagnetic valve that adjusts an amountof the working oil flowing into the working oil chamber by a degree ofopening of the electromagnetic valve; and a control unit that controlsthe degree of opening of the electromagnetic valve based on a weightexerted on the vehicle.
 2. The vehicle height adjustment apparatusaccording to claim 1, wherein the control unit changes upper and lowerlimits of the amount of working oil flowing into the working oil chamberbased on the weight exerted on the vehicle.